Polyamine-based corrosion inhibitors

ABSTRACT

Compounds having N-oxide, quaternary ammonium, and/or betaine functionality according to formulas (1)-(4) are effective corrosion inhibitors, suitable for use in any of a variety of applications such as automotive cooling systems, heating boilers, drilling of oil wells, and the handling, transportation and storage of crude petroleum and various petroleum fractions.  
                 
 
     The groups R 1 -R 5  may be certain hydrocarbyl groups. In formulas (1) and (3), R 3  may also be (CH 2 ) p —COO −  in which p is either 1 or 2, and R 2  may also be (CH 2 ) p —COO −  in formulas (3) and (4). In the compounds of formulas (1) and (2), R 2  may also be a polyhydroxyalkyl group of formula (A), shown below.

FIELD OF THE INVENTION

This invention relates to corrosion inhibitors. More particularly, itrelates to corrosion inhibitors comprising nitrogen functionality.

BACKGROUND OF THE INVENTION

Although significant effort has been directed toward development ofcorrosion-resistant alloys, prevention or inhibition of corrosion ofmetals remains a major concern. Reduction of corrosion is important inmany applications such as automotive cooling systems, heating boilers,drilling of oil wells, and the handling, transportation and storage ofcrude petroleum and various petroleum fractions. In these and otherapplications, corrosion often can have a significant economic impact interms of the maintenance, downtime, and replacement schedules requiredfor the associated equipment. Thus, prevention or inhibition ofcorrosion minimizes unscheduled shutdowns, maintenance and repair, andprovides for safer operation of the fluid handling equipment. To achievethis, one or more of additives referred to as corrosion inhibitors aretypically incorporated into the corrosive process streams to reducecorrosion. Although many corrosion inhibitors are known in the art,satisfactory corrosion inhibition is not always obtainable with existingsystems. Thus there is a continuing need for novel corrosion inhibitorssuitable for use in some or all of the above-mentioned environments, orothers.

SUMMARY OF THE INVENTION

In one aspect, the invention provides a compound according to formula(1)

wherein R₁ is selected from the group consisting of C₄-C₁₈ branchedalkyl, linear alkyl, alkenyl, cycloalkyl, aryl, alkaryl, and aralkyl; R₂is selected from the group consisting of C₁-C₈ alkyl, alkenyl,cycloalkyl, aryl, alkaryl, aralkyl, and moieties of formula (A)

R₃ is C₁-C₈ alkyl, alkenyl, cycloalkyl, aryl, alkaryl, or (CH₂)_(p)—COO⁻in which p is either 1 or 2; n is an integer from 2; to 14; m is aninteger from 0 to 2; R₄ is H, α-D-glucopyranosyl, β-D-pyranosyl, orβ-D-galactopyranosyl; and X⁻ is Cl⁻, Br, I⁻, OH⁻, CH₃COO⁻, 1/2 SO₄ ⁻²,or 1/3 PO₄ ⁻³, provided that the number of X⁻ moieties in formula (1) isreduced by one for each R₃ that is (CH₂)_(p)—COO⁻; further provided thatR₁ is not linear alkyl when R₃ is not (CH₂)_(p)—COO⁻.

In another aspect, the invention provides a compound according toformula (2)

wherein R₁ is selected from the group consisting of C₄-C₁₈ branchedalkyl, linear alkyl, alkenyl, cycloalkyl, aryl, alkaryl, and aralkyl; R₂is selected from the group consisting of C₁₋-C₁₈ alkyl, alkenyl,cycloalkyl, aryl, alkaryl, aralkyl, and moieties of formula (A)

n is an integer from 2 to 14; m is an integer from 0 to 2; and R₄ is H,α-D-glucopyranosyl, β-D-pyranosyl, or β-D-galactopyranosyl.

In yet another aspect, the invention provides a compound according toformula (3)

wherein R₁ is C₃-C₁₂ branched alkyl, linear alkyl, alkenyl, cycloalkyl,or aryl-substituted branched or linear alkyl; R₂ and R₃ are eachindividually selected from the group consisting of C₁-C₄ alkyl, benzyl,C₃-C₅ alkenyl, and (CH₂)_(p)—COO⁻ in which p is either 1 or 2, providedthat not both of R₂ and R₃ are (CH₂)_(p)—COO⁻; R₄ and R₅ are chosenindependently from C₂-C₆ alkylene; n is an integer from 0 to 4; and X⁻is Cl⁻, Br⁻, I⁻, OH⁻, CH₃COO⁻, 1/2 SO₄ ⁻², or 1/3 PO₄ ⁻³, provided thatthe number of X⁻ moieties in formula (3) is reduced by one for each R₃that is (CH₂)_(p)—COO⁻; further provided that, if n is 0 and R₄ is(CH₂)₂, then either R₁ is not linear alkyl or R₃ is (CH₂)_(p)—COO⁻, orboth.

In a further aspect, the invention provides a compound according toformula (4)

wherein R₁ is C₃-C₁₂ branched alkyl, linear alkyl, alkenyl, cycloalkyl,or aralkyl; R₂ is selected from the group consisting of C₁-C₄ alkyl,benzyl, C₃-C₅ alkenyl, and (CH₂)_(p)—COO⁻ in which p is either 1 or 2;R₄ and R₅ are chosen independently from C₂-C₆ alkylene; and n is aninteger from 0 to 4; provided that n is ≧1 if R₂ is not (CH₂)_(p)—COO⁻.

In a still further aspect, the invention provides a method of reducingcorrosion of a metal surface, comprising contacting the metal surfacewith a corrosive medium comprising a corrosion inhibitor according toany of formulas (1), (2), (3), and (4) shown above.

DETAILED DESCRIPTION OF THE INVENTION

This invention provides certain substituted alkylenediamines orpolyamines, and derivatives of these, suitable for use in preventing orinhibiting corrosion of metal surfaces in aqueous or other corrosiveenvironments. Four classes of compounds are provided, identified belowas formulas (1)-(4). Each of these will now be discussed in detail.

The first class of new corrosion inhibitors consists of certainderivatives of N,N′-dialkylalkylenediamines as shown below in formula(1).

In formula (1), R₁ is selected from the group consisting of C₄-C₁₈branched alkyl, linear alkyl, alkenyl, cycloalkyl, aryl, alkaryl, andaralkyl; R₂ is selected from the group consisting of C₁-C₈ alkyl,alkenyl, cycloalkyl, aryl, alkaryl, aralkyl and moieties of formula (A)

R₃ is C₁-C₈ alkyl, alkenyl, cycloalkyl, aryl, alkaryl, or (CH₂)_(p)—COO⁻in which p is either 1 or 2; n is an integer from 2 to 14; m is aninteger from 0 to 2; R₄ is H, α-D-glucopyranosyl, β-D-pyranosyl, orβ-D-galactopyranosyl; and X⁻ is Cl⁻, Br⁻, I⁻, OH⁻, CH₃COO⁻, 1/2 SO₄ ⁻²,or 1/3 PO₄ ⁻³, provided that the number of X⁻ moieties in formula (1) isreduced by one for each R₃ that is (CH₂)_(p)—COO⁻; further provided thatR₁ is not linear alkyl when R₃ is not (CH₂)_(p)—COO⁻. Substituents offormula (A) above, regardless of the identity of R₄, will be referred toherein as “polyhydroxyalkyl” groups. It will be understood to theartisan of ordinary skill in the art that the use of the term “2X⁻” informula (1) and in formula 1 (a) below is intended to indicate theamount of anion needed to provide charge neutrality.

Suitable exemplary R₁ groups include straight-chain or branched-chainalkyl groups such as n-butyl, 2-butyl, tert-butyl, isobutyl, n-pentyl,2-pentyl, tert-pentyl, isopentyl, neopentyl, 2-methylpentyl, n-hexyl,isohexyl, heptyl, 2-ethylhexyl, octyl, nonyl, 3,5-dimethyloctyl,3,7-dimethyloctyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl,3-methyl-10-ethyldodecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl,cocoalkyl (C₈H₁₇—C₁₆H₃₃), and tallow (C₁₆H₃₃—C₁₈H₃₇), as well asaralkyl, aryl, alkaryl, alicyclic, bicyclic, and similar groups.Examples of such groups are cyclohexylmethyl, benzyl, pinyl,pinylmethyl, phenethyl, p-methylbenzyl, phenyl, tolyl, xylyl, naphthyl,ethylphenyl, methylnaphthyl, dimethylnaphthyl, norbornyl, andnorbornylmethyl.

Suitable exemplary R₂ and R₃ groups include methyl, ethyl, n-propyl,isopropyl, n-butyl, 2-butyl, tert-butyl, isobutyl, n-pentyl, 2-pentyl,tert-pentyl, isopentyl, neopentyl, 2-methylpentyl, n-hexyl, isohexyl,heptyl, 2-ethylhexyl, octyl, cyclohexylmethyl, benzyl, phenethyl,p-methylbenzyl, phenyl, tolyl, xylyl, and ethylphenyl. Suitableexemplary R₂ groups also include polyhydroxyalkyl groups such as1-deoxyglucityl, 2,3-dihydroxypropyl, and analogous 1-deoxy groupsderived from mannitol, xylitol, galactitol, maltitol, and lactitol.

Compounds according to formula (1) may be prepared by any method knownin the synthetic organic chemical art. For example, they may be preparedby reaction of the corresponding N,N′-di(R₁)—N,N′-di(R₂)alkylenediaminewith an alkyl halide to introduce the group R₃, according to methodswell known in the chemical art. In the case where R₃ is (CH₂)_(p)—COO⁻,reaction with a halocarboxylic acid salt may be used, for example a saltof a haloacetic acid (see, e.g., Example 1 of U.S. Pat. No. 3,839,425;to E.I. DuPont de Nemours and Company).

If R₂ is a polyhydroxyalkyl group, a number of variations of R₂ arepossible, depending upon the value of R₄ and m, to form a variety ofcompounds according to formula (1a) below.

Compounds according to formula (1a) may be obtained by any suitableprocedure, for example that reported by V. I. Veksler, et. al., ZhurnalObshchei Khimii, 50(9), 2120-2123 (1980). Although any of a variety ofpolyhydroxyalkyl groups may be incorporated in compounds according tothe invention, they most typically will be derived from the open-chainforms of reducing sugars, for example glucose. Exemplarypolyhydroxyalkyl groups are derived from glucose; i.e., they are1-deoxyglucityl groups. In general, polyhydroxyalkyl groups ofN-(polyhydroxyalkyl)alkylamines useful for makingN,N′-dialkyl-N,N′-bis(polyhydroxyalkyl)alkylenediamines according to theinvention may be derived from any of the group of reducing sugarsconsisting of glucose, fructose, maltose, lactose, galactose, mannose,and xylose. Typically, the reducing sugar will be an aldose, althoughketoses may also be used, and both monosaccharides and disaccharides maybe used, with convenient sources of the latter including high dextrosecorn syrup, high fructose corn syrup, and high maltose corn syrup. Otheruseful polyhydroxyalkyl groups may be derived from glyceraldehydes. Insome embodiments, R₂ is a polyhydroxyalkyl group derived from glucose;i.e. the group is 1-deoxyglucityl. In this case, m is 2 and R₄ ishydrogen.

The second class of corrosion inhibitors includes bis N-oxides ofgeneral formula (2)

where R₁ and R₂ are as defined above in relation to compounds of formula(1).

Compounds according to formula (2) may be prepared by any method knownin the synthetic organic chemical art. For example, they may be preparedby treatment of the corresponding ditertiary amine with an oxidizingagent such as hydrogen peroxide (see, e.g., U.S. Pat. No. 5,710,332,Example 4, for preparation of N-oxides of N,N-dialkylglucamines).

The case where R₂ is a polyhydroxyalkyl group constitutes a subclass offormula (2), shown below as formula (2a), wherein R₁, R₄, m, and n havethe same meanings as defined above in relation to formula (1a).

In one embodiment, the polyhydroxyalkyl group is derived from glucose;i.e. the group is 1-deoxyglucityl. In this case, m is 2 and R₄ ishydrogen.

The third class of corrosion inhibitors consists of quaternaryderivatives of N,N′-dialkyl polyalkylene polyamines of general formula(3).

In formula (3), R₁ is C₃-C₁₂ branched alkyl, linear alkyl, alkenyl,cycloalkyl, or aryl-substituted branched or linear alkyl; R₂ and R₃ areeach individually selected from the group consisting of C₁-C₄ alkyl,benzyl, C₃-C₅ alkenyl, and (CH₂)_(p)—COO⁻ in which p is either 1 or 2,provided that not both of R₂ and R₃ are (CH₂)_(p)—COO⁻; R₄ and R₅ arechosen independently from C₂-C₆ alkylene; n is an integer from 0 to 4;and X⁻ is Cl⁻, Br⁻, I⁻, OH⁻, CH₃COO⁻, 1/2 SO₄ ⁻², or 1/3 PO₄ ⁻³,provided that the number of X⁻ moieties in formula (3) is reduced by onefor each R₃ that is (CH₂)_(p)—COO⁻. It will be understood to the artisanof ordinary skill in the art that the use of the term “(n+2)X⁻” informula (3) is intended to indicate the amount of anion needed toprovide charge neutrality.

In some embodiments of the invention, if n is 0 and R₄ is (CH₂)₂, theneither R¹ is not linear alkyl or R₃ is (CH₂)_(p)—COO⁻, or both. Suitableexemplary R₁ groups include straight-chain or branched-chain alkylgroups such as n-propyl, isopropyl, n-butyl, 2-butyl, tert-butyl,isobutyl, n-pentyl, 2-pentyl, tert-pentyl, isopentyl, neopentyl,2-methylpentyl, n-hexyl, isohexyl, heptyl, 2-ethylhexyl, octyl, nonyl,3,5-dimethyloctyl, 3,7-dimethyloctyl, decyl, undecyl, and dodecyl, aswell as cyclohexylmethyl, benzyl, phenethyl, and p-methylbenzyl.Suitable exemplary R₂ and R₃ groups include methyl, ethyl, n-propyl,isopropyl, n-butyl, 2-butyl, tert-butyl, isobutyl, and benzyl. In someembodiments, R₄ and R₅ are both (CH₂)₂, (CH₂)₃, (CH₂)₆, or(CH₂)₃CH(CH₃)CH₂.

Compounds according to formula (3) may be prepared by any method knownin the synthetic organic chemical art. For example, they may be preparedby alkylation under conditions known in the art of the correspondingpolyamine (4), which may in turn be obtained for example according toprocedures of any of U.S. Pat. No. 4,126,640; 4,195,152; or 6,015,852;

wherein R₁-R₅ are as defined for formula (3). Such alkylation may forexample be performed via reaction with an alkyl halide (see, e.g.,Synthetic Organic Chemistry, R. B. Wagner and H. D. Zook, John Wiley andSons, New York, 1953, p. 668). Compounds according to formula (4)themselves constitute a fourth class of corrosion inhibitors accordingto the invention, with R₁-R₅ and n being as defined above in relation toformula (3). In some embodiments, n is ≧1 if R₂ is not (CH₂)_(p)—COO⁻.In some embodiments, R₄ and R₅ are both (CH₂)₂, (CH₂)₃, (CH₂)₆, or(CH₂)₃CH(CH₃)CH₂.

The inhibitors of this invention can provide protection againstcorrosion to metals either on their own, or in any desired mixture withone another or with other inhibitors or inert or cooperative materials.Nonlimiting examples of such other ingredients include neutralizingamines, fatty amines, quaternary ammonium salts, imidazolines,imidazoles, alkynols, phosphonic acids, defoamers, and water or othersolvents. The amount of the inhibitors of this invention in such amixture can be varied over a range of 1 to 100 wt %, preferably 5 to 50wt %. Typically, mixtures containing the inhibitors are added at aconcentration of 1 to 5000 ppm by weight relative to a corrosive mediumthat contacts the metal surface, although concentrations in the rangefrom 1 to 100 ppm are more typical. Corrosive media may be aqueous orliquid organic media, or they may contain both aqueous and organiccomponents in a mixture that may be a solution, a suspension, or acombination of these. Examples of corrosive media that may be treatedwith the corrosion inhibitors include automotive cooling systems,heating boilers, drilling of oil wells, and the handling,transportation, and storage of crude petroleum and various petroleumfractions.

A typical aqueous corrosion inhibitor formulation for treatment ofboiler water or steam condensates that includes the corrosion inhibitorsof the invention may include the following components by weight:

-   -   1-20% compounds according to any of formulas (1), (2,), (3), and        (4);    -   4-40% of one or more basic neutralizing compounds, for example        NaOH, KOH, phosphates, silicates, carbonates, borates, ammonia,        ammonium salts, neutralizing amines, and volatile amines such as        cyclohexylamine, morpholine, dicyclohexylamine, and        diethylaminoethanol;    -   0-20% film-forming amines such as octadecylamine, tallowamines,        cocoamines, oleylamines, amidoamines, imidazolines, fatty        alkylamines or diamines, and quaternary salts of these or salts        of these with organic or inorganic acids;    -   0-10% one or more other active ingredients such as oxygen        scavengers, scale inhibitors, chelating agents, dispersants,        emulsifiers, surfactants, and water-soluble polymers; and 10-95%        water.

A typical corrosion inhibitor formulation for metal working, metaltreatment or metal lubricants that includes the corrosion inhibitors ofthe invention may include the following components by weight:

-   -   30-99% one or more carriers or solvents, for example hydrocarbon        solvents or oils or waxes, mineral oils or waxes, synthetic        esters or polyesters, polyethers, alcohols, water, and natural        fats or oils such as tall oil, rapeseed oil, corn oil, castor        oil, cottonseed oil, palm oil, lard oil, and tallow;    -   1-20% compounds according to any of formulas (1), (2,), (3), and        (4);    -   0-20% co-corrosion Inhibitors such as organic acids and their        mineral or amine salts, organo-boron compounds or salts,        octadecylamine, tallowamines, cocoamines, oleylamines,        amidoamines, imidazolines, alkanolamides, sulfonamides, fatty        alkylamines or diamines, and quaternary salts of these or salts        of these with organic or inorganic acids;    -   0-20% basic neutralizing compounds such as neutralizing amines,        alkylamines, alkylalkanolamines, alkanolamines, and alkaline        salts; and    -   0-10% one or more other active ingredients such as water        repellents, antioxidants, lubricants, emulsifiers, surfactants,        defoamers, biocides, and stabilizers.

A typical corrosion inhibitor formulation for oil field, petroleumtransportation, or refinery applications that includes the corrosioninhibitors of the invention may include the following components byweight:

-   -   20-99% one or more carriers or solvents such as hydrocarbon        solvents or oils, water, and dispersing or coupling agents such        as glycols, glycol ethers, alcohols, esters, ketones, amides,        surfactants, emulsifiers, or dispersants;    -   1-30% compounds according to any of formulas (1), (2,), (3), and        (4);    -   0-30% one or more co-corrosion inhibitors, such as organic acids        and their mineral or amine salts, organophosphonates, phosphate        esters, alkynols; neutralizing inhibitors such as alkaline        salts, ammonia, ammonium salts, and neutralizing amines;        volatile amines such as cyclohexylamine, morpholine,        alkylamines, alkylalkanQlamines and alkanolamines;        octadecylamine, tallowamines, cocoamines, oleylamines,        amidoamines, imidazolines, alkyl pyridines, amides and their        salts, fatty alkylamines or diamines, and quaternary salts of        these or salts of these with organic or inorganic acids; and    -   0-20% one or more other active ingredients such as        nonemulsifiers, antifoams, surfactants, biocides, oxygen        scavengers, hydrogen sulfide scavengers, and scale inhibitors.

In addition to their activity as corrosion inhibitors, compounds (1a)and (2a) of the present invention may exhibit increased biodegradationand lower aquatic toxicity relative to inhibitors of the prior art. Moregenerally, inhibitors (1), (2), (3), and (4) of the present invention,being diamine or polyamine compounds, may exhibit lower aquatic toxicityrelative to some existing inhibitors.

The invention is further illustrated by the following examples, whichare presented for purposes of demonstrating, but not limiting, themethods and compositions of this invention.

EXAMPLES

Example 1 illustrates preparation ofN,N′-dimethyl-N,N′-dilaurylethylenediamine, an example of anintermediate in the synthesis of class corrosion inhibitors of formula(1). Examples 2-10 illustrate preparation of otherN,N′-di(R₁)-N,N′-di(R₂)alkylenediamines.

Examples 1-10

A 300 mL Autoclave Engineers stainless steel reactor was charged with72.4 g (0.40 mole) lauronitrile, 16.8 g (0.19 mole) ofN,N′-dimethylethylenediamine, 1.45 g (dry weight basis) of a 5%palladium-on-carbon catalyst, and 48 g of isopropanol. The reactor wasclosed, purged with nitrogen and hydrogen, and pressurized to about 600psig with hydrogen. The mixture was heated with stirring (1000 rpm) to125° C., pressurized with hydrogen to 1000 psig, and maintained at thistemperature and pressure via regulated hydrogen feed. After 7 hr, themixture was cooled to room temperature and the product was removed fromthe reactor with filtering through an internal 0.5 μm sintered metalelement. Analysis of the product by GC (Gas Chromatography) and GC-MS(Gas Chromatography-Mass Spectrometry) indicated that conversion wascomplete, and that the product consisted of 98+%N,N′-dimethyl-N,N′-dilaurylethylenediamine and just over 1% ofN,N′-dimethyl-N-laurylethylenediamine. Vacuum distillation (190-200°C./80-100 Torr) provided pureN,N′-dimethyl-N,N′-dilaurylethylenediamine. AdditionalN,N′-di(R₁)-N,N′-di(R₂)alkylenediamines may be prepared andcharacterized using procedures similar to those described above. Some ofthese diamines are shown as Examples 2-10 in Table 1. TABLE 1

Example R₁ R₂ n 1 C₁₂H₂₅ CH₃ 2 2 C₆H₁₁ C₂H₅ 2 3 C₆H₁₁ C₂H₅ 6 4 C₈H₁₅ CH₃2 5 C₈H₁₅ CH₃ 6 6 C₁₀H₂₁ CH₃ 2 7 C₁₂H₂₅ C₂H₅ 2 8 Cocoalkyl CH₃ 2(C₈H₁₇—C₁₆H₃₃) 9 Cocoalkyl C₂H₅ 2 (C₈H₁₇—C₁₆H₃₃) 10 Tallow CH₃ 2(C₁₆H₃₃—C₁₈H₃₇)

Examples 11-15 illustrate preparation of bis betaine salts, i.e.,examples of the class (1) of corrosion inhibitor where R₃ is(CH₂)_(p)—COO⁻, and specifically of Example 11 in Table 2.

Examples 11-15

To a 250 mL three-necked flask equipped with a magnetic stirrer, refluxcondenser, thermometer and nitrogen purge were added 20 g (0.0472 mole)of N,N′-dimethyl-N,N′-dilaurylethylenediamine, 25.54 g (0.1180 mole) ofsodium iodoacetate, 80 mL of isopropanol, and 8 mL of deionized water atambient temperature. The mixture was heated with stirring to 80° C. andmaintained at that temperature for 4.5 hrs. After cooling to roomtemperature, the solvent was removed under vacuum with a rotaryevaporator. Addition of isopropanol (about 100 mL), vacuum filtration,and subsequent removal of isopropanol under vacuum with a rotaryevaporator yielded pureN,N′-di(carboxymethyl)-N,N′-dimethyl-N,N′-dilaurylethylenediammoniumdihydroxide inner salt. Additional bis betaines may be prepared andcharacterized using procedures similar to those described above. Some ofthese are shown in Table 2, wherein X is I in all examples. TABLE 2

Example R₁ R₂ R₃ n 11 C₁₂H₂₅ CH₃ CH₂COO— 2 12 C₆H₁₁ C₂H₅ CH₂COO— 2 13C₈H₁₅ CH₃ 2 14 Cocoalkyl CH₃ CH₂COO— 2 (C₈H₁₇—C₁₆H₃₃) 15 Tallow CH₃CH_(COO—) 2 (C₁₆H₃₃—C₁₈H₃₇)

Examples 16-20 illustrate preparation of several bis N-oxides, examplesof class (2) corrosion inhibitors in which none of the substituents oneither nitrogen is a polyhydroxyalkyl group.

Examples 16-20

To a 100 mL three-necked flask equipped with a magnetic stirrer, refluxcondenser, thermometer, septum and nitrogen purge were added 5 g (0.0118mole) of N,N′-dimethyl-N,N′-laurylethylenediamine and 25 mL ofisopropanol at ambient temperature. The mixture was heated with stirringto 60° C., after which 3.2 g (0.028 mole; 2.4 eq.) of 30 wt % aqueoushydrogen peroxide was added dropwise from a syringe. The reaction wasmaintained at 60° C. for 6 hrs. After cooling to room temperature,removal of the solvent under vacuum with a rotary evaporator yieldedN,N′-dimethyl-N,N′-dilaurylethylenediamine-N,N′-bis(N-oxide). Theidentity and purity of the product were determined by NMR analysis.Additional analogous alkylenediamine bis(N-oxides) may be prepared andcharacterized using procedures similar to those described above. Some ofthese are shown in Table 3. TABLE 3

Example R₁ R₂ n 16 C₁₂H₂₅ CH₃ 2 17 C₆H₁₁ C₂H₅ 2 18 C₈H₁₅ CH₃ 2 19Cocoalkyl CH₃ 2 (C₈H₁₇—C₁₆H₃₃) 20 Tallow CH₃ 2 (C₁₆H₃₃—C₁₈H₃₇)

Examples 21-24 illustrate preparation of several bis N-oxides in whichboth nitrogen atoms are substituted with polyhydroxyalkyl groups; i.e.compounds of subclass (2a).

Examples 21-24

The procedure of Example 20 is repeated withN,N′-dioctyl-N,N′-bis(1-deoxyglucityl)ethylenediamine, with use ofmethanol rather than isopropanol as solvent, to prepare the compoundsshown in Table 4, where R₄═H and m and n are both 2. TABLE 4

Example R₁ 21 C₈H₁₇ 22 C₆H₁₁ 23 C₄H₉ 24 C₁₂H₂₅

Example 25 and 26 illustrate the use of certain exemplary compounds ofthe invention as corrosion inhibitors.

Example 25 Control (No Inhibitor)

Rate of corrosion were determined by an electrochemical potentiodynamictechnique. The apparatus was a standard three-electrode electrochemicalcell with the specimen or working electrode fabricated from 1018 carbonsteel solid rod. A solution to working electrode surface area ratio of190 mL/cm² was used for testing. Polarization was started at 250 mVbelow (more active than) open circuit potential (E_(∝) after 1 hr) andscanned in the positive direction at a rate of 0.6 V/hour to 250 mVabove E_(∝). Current was recorded continuously. Corrosion potential(E_(corr)) and corrosion current (I_(corr)) were derived from thepolarization curve (E vs. Log I) using Tafel Analysis. The corrosionrate, expressed in mils per year (mpy), was calculated from thecorrosion current. Corrosion testing was performed using a simulatedbrine solution, prepared by mixing 85.07 g calcium chloride dihydrate,39.16 g magnesium chloride hexahydrate, 2025.00 g sodium chloride, and19L of distilled water according to NACE Test Method 1D196. For thisexample volume of simulated brine solution required for a solution toworking electrode surface area ratio of 190 mL/cm² was held in theelectrochemical testing apparatus at a temperature of 120 (±2)° F. Thebrine solution was sparged continuously with gaseous carbon dioxide for2 hours prior to and during testing. With no added inhibitor, acorrosion rate of 47.7 mpy was determined for a test substrate of 1018carbon steel.

Example 26 Corrosion Inhibitors of Classes (1), (2), (3), and (4)

Corrosion performance is determined using the general procedure ofExample 25, but 100 ppm of a compound of Type (1), (1a), (2), (2a), (3)or (4), by weight relative to the brine solution is added to theelectrochemical testing apparatus prior to measurement. A corrosion rateof <25 mpy is determined for a test substrate of 1018 carbon steel.

Uses of Compounds of Formula (1)-(4)

Compounds according to any of the four classes described above may beincorporated into compositions including any of a wide variety of otheringredients designed to complement their utility as corrosioninhibitors. The performance properties of such products may be optimizedfor a specific application by appropriate modification of the structureof the inhibitor and the choice of the substituents R₁, R₂, R₃, R₄, andR₅, the number of repeating units m or n in the linking groups, and thelength of the alkylene groups between the nitrogen atoms. Suchoptimization is routine, and within the ability of the person ofordinary skill in the art in the particular application area. Thusmanipulation of these variables yields compounds which may find utilityas corrosion inhibitors in a variety of applications, including forexample thbse outlined in the foregoing disclosure.

Although the invention is illustrated and described herein withreference to specific embodiments, it is not intended that the subjoinedclaims be limited to the details shown. Rather, it is expected thatvarious modifications may be made in these details by those skilled inthe art, which modifications may still be within the spirit and scope ofthe claimed subject matter and it is intended that these claims beconstrued accordingly.

1. A compound according to formula (1)

wherein R₁ is selected from the group consisting of C₄-C₁₈ branchedalkyl, linear alkyl, alkenyl, cycloalkyl, aryl, alkaryl, and aralkyl; R₂is selected from the group consisting of C₁-C₈ alkyl, alkenyl,cycloalkyl, aryl, alkaryl, aralkyl, and moieties of formula (A)

R₃ is C₁-C₈ alkyl, alkenyl, cycloalkyl, aryl, alkaryl, or (CH₂)_(p)—COO⁻in which p is either 1 or 2; n is an integer from 2 to 14; m is aninteger from 0 to 2; R₄ is H, α-D-glucopyranosyl, β-D-pyranosyl, orβ-D-galactopyranosyl; and X⁻ is Cl⁻, Br⁻, I⁻, OH⁻, CH₃COO⁻, 1/2 SO₄ ⁻²,or 1/3 PO₄ ⁻³, provided that the number of X⁻ moieties in formula (1) isreduced by one for each R₃ that is (CH₂)_(p)—COO⁻; further provided thatR₁ is not linear-alkyl when R₃ is not (CH₂)_(p)—COO⁻.
 2. The compound ofclaim 1, wherein R₁ is a moiety of formula (A).
 3. The compound of claim1, wherein R₁ is dodecyl.
 4. The compound of claim 1, wherein R₁ iscocoalkyl.
 5. The compound of claim 1, wherein R₁ is tallow.
 6. Thecompound of claim 1, wherein R₂ is 1-deoxyglucityl.
 7. The compound ofclaim 1, wherein R₂ is methyl or ethyl.
 8. The compound of claim 1,wherein R₃ is (CH₂)_(p)—COO⁻.
 9. The compound of claim 1, wherein n is 2or
 6. 10. A compound according to formula (2)

wherein R₁ is selected from the group consisting of C₄-C₁₈ branchedalkyl, linear alkyl, alkenyl, cycloalkyl, aryl, alkaryl, and aralkyl; R₂is selected from the group consisting of C₁-C₈ alkyl, alkenyl,cycloalkyl, aryl, alkaryl, aralkyl, and moieties of formula (A)

n is an integer from 2 to 14; m is an integer from 0 to 2; and R₄ is H,α-D-glucopyranosyl, β-D-pyranosyl, or β-D-galactopyranosyl.
 11. Thecompound of claim 10, wherein R₁ is dodecyl.
 12. The compound of claim10, wherein R₁ is cocoalkyl.
 13. The compound of claim 10, wherein R₁ istallow.
 14. The compound of claim 10, wherein R₂ is methyl or ethyl. 15.The compound of claim 10, wherein R₂ is a moiety of formula (A).
 16. Thecompound of claim 10, wherein R₂ is 1-deoxyglucityl.
 17. The compound ofclaim 16, wherein R₁ is selected from the group consisting of butyl,hexyl, octyl, and dodecyl.
 18. The compound of claim 10, wherein n is 2or
 6. 19. A compound according to formula (3)

wherein R₁ is C₃-C₁₂ branched alkyl, linear alkyl, alkenyl, cycloalkyl,or aryl-substituted branched or linear alkyl; R₂ and R₃ are eachindividually selected from the group consisting of C₁-C₄ alkyl, benzyl,C₃-C₅ alkenyl, and (CH₂)_(p)—COO⁻ in which p is either 1 or 2, providedthat not both of R₂ and R₃ are (CH₂)_(p)—COO⁻; R₄ and R₅ are chosenindependently from C₂-C₆ alkylene; n is an integer from 0 to 4; and X⁻is Cl⁻, Br⁻, I⁻, OH⁻, CH₃COO⁻, 1/2 SO₄ ⁻², or 1/3 PO₄ ⁻³, provided thatthe number of X moieties in formula (3) is reduced by one for each R₃that is (CH₂)_(p)—COO⁻; further provided that, if n is 0 and R₄ is(CH₂)₂, then either R₁ is not linear alkyl or R₃ is (CH₂)_(p)—COO⁻, orboth.
 20. The compound of claim 19, wherein R₁ is branched C₃-C₁₂ alkyl.21. The compound of claim 19, wherein R₃ is (CH₂)_(p)—COO⁻.
 22. Thecompound of claim 19, wherein R₄ and R₅ are both (CH₂)₂.
 23. Thecompound of claim 19, wherein R₄ and R₅ are both (CH₂)₃.
 24. Thecompound of claim 19, wherein R₄ and R₅ are both (CH₂)₆.
 25. Thecompound of claim 19, wherein R₄ and R₅ are both (CH₂)₃CH(CH₃)CH₂.
 26. Acompound according to formula (4)

wherein R₁ is C₃-C₁₂ branched alkyl, linear alkyl, alkenyl, cycloalkyl,or aralkyl; R₂ is selected from the group consisting of C₁-C₄ alkyl,benzyl, C₃-C₅ alkenyl, and (CH₂)_(p)—COO⁻ in which p is either 1 or 2;R₄ and R₅ are chosen independently from C₂-C₆ alkylene; and n is aninteger from 0 to 4; provided that n is ≧1 if R₂ is not (CH₂)_(p)—COO⁻.27. The compound of claim 26, wherein R₄ and R₅ are both (CH₂)₂.
 28. Thecompound of claim 26, wherein R₄ and R₅ are both (CH₂)₃.
 29. Thecompound of claim 26, wherein R₄ and R₅ are both (CH₂)₆.
 30. Thecompound of claim 26, wherein R₄ and R₅ are both (CH₂)₃CH(CH₃)CH₂.
 31. Amethod of reducing corrosion of a metal surface, comprising contactingthe metal surface with a corrosive medium comprising a corrosioninhibitor according to any of: a) formula (1):

wherein R₁ is selected from the group consisting of C₄-C₁₈ branchedalkyl, linear alkyl, alkenyl, cycloalkyl, aryl, alkaryl, and aralkyl; R₂is selected from the group consisting of C₁₋C₈ alkyl, alkenyl,cycloalkyl, aryl, alkaryl, aralkyl, and moieties of formula (A)

R₃ is C₁-C₈ alkyl, alkenyl, cycloalkyl, aryl, alkaryl, or (CH₂)_(p)—COO⁻in which p is either 1 or 2; n is an integer from 2 to 14; m is aninteger from 0 to 2; R₄ is H, α-D-glucopyranosyl, β-D-pyranosyl, orβ-D-galactopyranosyl; and X⁻ is Cl⁻, Br⁻, I⁻, OH⁻, CH₃COO⁻, 1/2 SO₄ ⁻²,or 1/3 PO₄ ⁻³, provided that the number of X⁻ moieties in formula (1) isreduced by one for each R₃ that is (CH₂)_(p)—COO⁻; further provided thatR₁ is not linear alkyl when R₃ is not (CH₂)_(p)—COO⁻; b) formula (2):

wherein R₁ is selected from the group consisting of C₄-C₁₈ branchedalkyl, linear alkyl, alkenyl, cycloalkyl, aryl, alkaryl, and aralkyl; R₂is selected from the group consisting of C1-C8 alkyl, alkenyl,cycloalkyl, aryl, alkaryl, aralkyl, and moieties of formula (A)

n is an integer from 2 to 14; m is an integer from 0 to 2; and R₄ is H,α-D-glucopyranosyl, β-D-pyranosyl, or β-D-galactopyranosyl; c) formula(3):

wherein R₁ is C₃-C₁₂ branched alkyl, linear alkyl, alkenyl, cycloalkyl,or aryl-substituted branched or linear alkyl; R₂ and R₃ are eachindividually selected from the group consisting of C₁-C₄ alkyl, benzyl,C₃-C₅ alkenyl, and (CH₂)_(p)—COO⁻ in which p is either 1 or 2, providedthat not both of R₂ and R₃ are (CH₂)_(p)—COO⁻; R₄ and R₅ are chosenindependently from C₂-C₆ alkylene; n is an integer from 0 to 4; and X⁻is Cl⁻, Br⁻, I⁻, OH⁻, CH₃COO⁻, 1/2 SO₄ ⁻², or 1/3 PO₄ ⁻³, provided thatthe number of X⁻ moieties in formula (3) is reduced by one for each R₃that is (CH₂)_(p)—COO⁻; further provided that, if n is 0 and R₄ is(CH₂)₂, then either R₁ is not linear alkyl or R₃ is (CH₂)_(p)—COO⁻, orboth; and d) formula (4):

wherein R₁ is C₃-C₁₂ branched alkyl, linear alkyl, alkenyl, cycloalkyl,or aralkyl; R₂ is selected from the group consisting of C₁-C₄ alkyl,benzyl, C₃-C₅ alkenyl, and (CH₂)_(p)—COO⁻ in which p is either 1 or 2;R₄ and R₅ are chosen independently from C₂-C₆ alkylene; and n is aninteger from 0 to 4; provided that n is ≧1 if R₂ is not (CH₂)_(p)—COO⁻.